The proposed research will continue an analysis of the properties of brainstem and diencephalic neurons responsive to genital stimulation (genitally-sensitive neurons) in the female cat. Through the use of chronic recording methods the activity of single-units and unit clusters will be examined during the elicitation of behavioral responses to genital stimulation in ovariectomized anestrous, and estrogen-treated cats. The objective is an identification of differences in the activity of these neurons in the estrous and anestrous conditions in order to elucidate the neural basis of estrogen-dependent behavioral responses to genital stimulation. In a parallel series of experiments on acutely-prepared cats, single-unit recording and neuroanatomical methods will be employed to analyze the neuronal circuitry and hormone-dependent neural activity patterns mediating the estrous cry and after-reaction responses of the estrous cat to genital stimulation. Investigations will also be initiated on female hamsters with the objective of identifying estrogen and progesterone effects on brainstem neurons responsive to tactile stimulation of lordosis-eliciting skin field. As in the cat experiments, work on the hamsters will entail single-unit recording in behaving as well as acutely-prepared animals. The results of this research should reveal some of the ways in which ovarian hormones act upon neurons in the brain to modify behavioral responses to the sensory stimuli which occur during mating.